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Re: [Xen-users] CoW works on Windows guest?

To: "Orathai Sukwong" <kobkob@xxxxxxxxx>
Subject: Re: [Xen-users] CoW works on Windows guest?
From: Dan Smith <danms@xxxxxxxxxx>
Date: Thu, 28 Sep 2006 17:08:34 -0700
Cc: Ryan Grimm <grimm@xxxxxxxxxx>, xen-users@xxxxxxxxxxxxxxxxxxx
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In-reply-to: <748f85310609281151q586a21b7if3a97e384f59eae9@xxxxxxxxxxxxxx> (Orathai Sukwong's message of "Thu, 28 Sep 2006 14:51:52 -0400")
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OS> My current dom0 was compiled from xen-3.0.2-2 source + dm
OS> patches. I cannot find the cowd daemon. I wonder if it is
OS> something I need to compile separately.

If you applied the dm-userspace patches to your xen tree and either
rebuilt and installed the whole tree, or at least the tools part, you
should have "dscow_tool" and "cowd" binaries on your system.  If you
don't see them, check in the tools/ directory of your tree

OS> Which device do you mean for the target device? Previously, my
OS> installation configuration file was like disk = ["file:/xenimages/
OS> windowsbase.img,ioemu:hda,w" ]. Then, I changed to disk =
OS> ["dmu:dscow:/tmp/
OS> windowsbase.dscow:/xenimages/windowsbase.img,ioemu:hda,w" ]. Is
OS> the /tmp/ windowsbase.dscow what you meant?

Do this:

  # dscow_tool -c /xenimages/windowsbase.dscow /xenimages/windowsbase.img

Which will create the cow file.  Then do:

  # cowd -p --sync=a dscow windowsbase /xenimages/windowsbase.dscow

Which will create a /dev/mapper/windowsbase device.  Any writes to
this device will be stored in the .dscow file; the .img file will
remain untouched.  Then, configure your domain to use the new device
with something like this:

  disk = [ '/dev/mapper/windowsbase,ioemu:hda,w' ]

(I'm not all that familiar with HVM config files, so adjust the above
line as appropriate)

Note that all the above assumes you have the dm-user.ko module
loaded.  If you built and installed Xen with the dm-userspace patches,
you should be able to just do:

  # modprobe dm-user

Dan Smith
IBM Linux Technology Center
Open Hypervisor Team
email: danms@xxxxxxxxxx

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